Implement serf_request_read_iovec to further condense TCP writev() calls.
Implement serf_request_read_iovec to further condense TCP writev() calls.

* buckets/request_buckets.c
  (serf_request_read_iovec): Implement.
  (serf_bucket_type_request): Delegate to the aggregate bucket directly
  instead of letting a level of indirection separate the read() passes.


git-svn-id: 683495cb1553624b05a54e2ba9533425f69cf277@1098 61a7d7f5-40b7-0310-9c16-bb0ea8cb1845

coapp-packages/serf,coapp-packages/serf,coapp-packages/serf